Semiconductor waveguide-based avalanche photodetector with separate absorption and multiplication regions

Abstract

A semiconductor waveguide based optical receiver is disclosed. An apparatus according to aspects of the present invention includes an absorption region defined along an optical waveguide. The absorption region includes a first type of semiconductor material having a first refractive index. The apparatus also includes a multiplication region defined along the optical waveguide. The multiplication region is proximate to and separate from the absorption region. The multiplication region includes a second type of semiconductor material having a second refractive index. The first refractive index greater than the second refractive index such that an optical beam directed through the optical waveguide is pulled towards the absorption region from the multiplication region and absorbed in the absorption region to create electron-hole pairs from the optical beam. The multiplication region includes first and second doped regions defined along the optical waveguide. The first and second doped regions have opposite polarity to create an electric field to multiply the electrons created in the absorption region.

1. An apparatus, comprising:
 an absorption region defined along an optical waveguide, the absorption region comprising a first type of semiconductor material having a first refractive index; and 
 a multiplication region defined along the optical waveguide proximate to and separate from the absorption region, the multiplication region comprising a second type of semiconductor material having a second refractive index, the first refractive index greater than the second refractive index such that an optical beam directed through the optical waveguide is pulled towards the absorption region from the multiplication region and absorbed in the absorption region to create electron-hole pairs from the optical beam, the multiplication region including first and second substantially doped regions physically abutting each other defined along the optical waveguide, the first and second doped regions having opposite polarity to create an electric field to multiply the electrons created in the absorption region. 
 
   
   
     2. The apparatus of  claim 1  wherein the first type of semiconductor material substantially comprises germanium. 
   
   
     3. The apparatus of  claim 1  wherein the first refractive index is approximately equal to 4. 
   
   
     4. The apparatus of  claim 1  wherein the optical beam absorbed in the absorption region comprises light having a wavelength of approximately 1300 or 1550 nanometers. 
   
   
     5. The apparatus of  claim 1  wherein the second type of semiconductor material substantially comprises silicon. 
   
   
     6. The apparatus of  claim 1  wherein the second refractive index is approximately equal to 3.5. 
   
   
     7. The apparatus of  claim 1  wherein the second type of semiconductor material has a k-factor value less than approximately 0.05 such that the electrons created in the absorption region are selectively multiplied in the multiplication region instead of the holes created in the absorption region. 
   
   
     8. The apparatus of  claim 1  wherein the first and second doped regions comprise p-doped and n-doped regions of silicon. 
   
   
     9. The apparatus of  claim 1  wherein the optical beam comprises infrared or near infrared light. 
   
   
     10. A system, comprising:
 an optical source to generate an optical beam having an infrared or near infrared wavelength; 
 an optical fiber optically coupled to receive the optical beam from the optical source; and 
 an optical receiver optically coupled to receive the optical beam from the optical fiber; the optical receiver including: 
 an absorption region defined along an optical waveguide in semiconductor material, the absorption region comprising a first type of semiconductor material having a first refractive index; and 
 a multiplication region defined along the optical waveguide, multiplication region proximate to and separate from the absorption region, the multiplication region comprising a second type of semiconductor material having a second refractive index, the first refractive index greater than the second refractive index such that the optical beam received by the optical receiver is directed through the optical waveguide and is pulled towards the absorption region from the multiplication region and absorbed in the absorption region to create electron-hole pairs from the optical beam, the multiplication region including first and second substantially doped regions physically abutting each other defined along the optical waveguide, the first and second doped regions having opposite polarity to create an electric field to multiply the electrons created in the absorption region. 
 
   
   
     11. The system of  claim 10  wherein the first type of semiconductor material substantially comprises germanium and the second type of semiconductor material substantially comprises silicon. 
   
   
     12. The system of  claim 10  further comprising a optical beam comprises light having a wavelength of approximately 1300 or 1550 nanometers. 
   
   
     13. The system of  claim 10  wherein the optical receiver further includes an optical filter defined along the optical waveguide in the semiconductor material. 
   
   
     14. The system of  claim 10  wherein the optical receiver further includes an optical attenuator defined along the optical waveguide in the semiconductor material. 
   
   
     15. An apparatus, comprising:
 an absorption region defined along an optical waveguide, the absorption region comprising a first type of semiconductor material having a first refractive index; 
 a multiplication region defined along the optical waveguide proximate to and separate from the absorption region, the multiplication region comprising a second type of semiconductor material having a second refractive index, the first refractive index greater than the second refractive index such that an optical beam directed through the optical waveguide is pulled towards the absorption region from the multiplication region and absorbed in the absorption region to create electron-hole pairs from the optical beam, the multiplication region including first and second doped regions defined along the optical waveguide, the first and second doped regions having opposite polarity to create an electric field to multiply the electrons created in the absorption region; and 
 an intervening layer defined along the optical waveguide between the absorption region and the multiplication region, the intervening layer comprising the second type of semiconductor material and being substantially intrinsic. 
 
   
   
     16. The apparatus of  claim 15  wherein the first type of semiconductor material substantially comprises germanium and the second type of semiconductor material substantially comprises silicon.